The present invention relates to a tape transport apparatus with a reduced widths which apparatus is used with a cartridge having an internal drive roller. More particularly, the invention relates to a tape transport apparatus in which a pulley and pulley drive motor are mounted to the same base.
In tape recorders, data recorders, and other conversational devices using cartridges which store information recording tapes (magnetic tapes and the like), the tape transport apparatus causes the information recording tape to run. For example, the information recording tape is mounted onto reels inside the cartridge and the tape transport apparatus rotationally drives the reels from outside the cartridge so that the information recording tape runs, and the recording of information to and/or playback from the information recording tape (hereinafter termed magnetic tape) is performed.
FIG. 6 is a perspective view showing an outer view of a data cartridge. Internal to the data cartridge 1 is a drive roller 4. This is rotationally driven from outside so that the tape inside the cartridge runs.
As shown in FIG. 6, a window opening 2a is formed on the center portion at an intersection of a side and a front surface of a case 2. To the left side of the front surface of the case 2 is provided a cover 3 adjacent to the window opening 2a. The drive roller 4 is provided internal to the case 2, and the peripheral surface 4a of the drive roller 4 is exposed from the window opening 2a. The cover 3 is supported by the corner of the left side of the front surface of the case 2 and is freely rotatable.
The cover 3 is normally closed in order to prevent entry of dust into the case 2. When the distal end portion 3a of the cover 3 is pressed, the cover 3 rotates about the center of a support shaft 3b shown in FIG. 7 and opens. Then, a magnetic tape (not shown in the figure) stored inside the case 2 is exposed from the opening portion and the exposed magnetic tape comes into contact with a magnetic head not shown in FIG. 7.
FIG. 7 is a plan view showing the internal configuration of the data cartridge. Inside the case 2 of the data cartridge 1 are provided a pair of reels 6 and 7, a pair of guide rollers 8 and 9, a pair of tension rollers 10 and 11 and the drive roller 4. The respective reels and rollers are supported on shafts so as to be freely rotatable.
A drive belt 12 is mounted on the drive roller 4, and the guide rollers 8 and 9. This drive belt 12 presses against the front surfaces of magnetic tape reels 5a and 5b wound around the reels 6 and 7.
In the data cartridge 1 with the above described structure, external rotational force is transmitted to the drive roller 4, and rotation of the drive roller 4 makes a magnetic tape 5 run inside the case 2 as described below.
More specifically, when the drive roller 4 rotates clockwise, the drive belt 12 moves in the direction shown by the arrow E. Hence, the forces F1 and F2 in the direction of the line of contact are applied to the peripheral portion of the magnetic tape reels 5a and 5b that are wound to the reels 6 and 7.
As a result, reels 6 and 7 both rotate counter-clockwise, and the magnetic tape 5 is wound from the reel 6 to the other reel 7. The magnetic tape 5 runs in the direction shown by the arrow D, between the tension rollers 10 and 11. When this occurs, the magnetic tape 5 does not contact the drive belt 12 that is wound to the drive roller 4.
FIG. 8 is a plan view showing one example of a conventional tape transport apparatus. FIG. 9 is a sectional view along the sectional line VIII--VIII of FIG. 8. In both figures, the state where the data cartridge 1 is mounted is shown by a solid line, and, in FIG. 8, the state where the data cartridge 1 is partially mounted is shown by a broken line.
As shown in both of these figures, a tape transport mechanism 20 has a circuit board 25, a magnetic head 24, a drive unit 30, and a mounting portion 22 inside a transport apparatus main unit 21. The data cartridge 1 is inserted to or withdrawn from the mounting portion 22, in a direction, as shown by the arrow A-B from outside the transport apparatus main unit 21.
The magnetic head 24 comes into contact with the magnetic tape 5 inside the data cartridge 1 and the recording of information to and/or playback from the information recording tape is performed. To the magnetic head 24 are supplied recording signals from the circuit board 25 and the reproduction signals from the magnetic head 24 are output to the circuit board 25 and processed.
The drive unit 30 has a pulley 31. This pulley 31 contacts the drive roller 4 of the data cartridge 1 and rotates, causing the drive roller 4 to also rotate. In FIG. 9, above this pulley 31 is provided a roller 32 which is on the same shaft as the pulley 31. The pulley 31 and the roller 32 are supported by a rotating shaft 33 supported by a support member 38 and are freely rotatable.
A roller 35 is inserted into a rotating shaft 34a of a drive motor 34 and is fixed. A belt 36 is wound to the roller 35 and the roller 32. The rotational force of the drive motor 34 is thus transmitted to the pulley 31 via the roller 35, the belt 36 and the roller 32.
The support member 38 is supported by a rotating shaft 37 and the rotating shaft 37 is provided on the transport apparatus main unit 21. Accordingly, the support member 38 is freely rotatable with respect to the transport apparatus main unit 21. Between the support member 38 and the transport apparatus main unit 21 is provided a spring (not shown in the figure). In FIG. 8, the support member 38 is urged by the spring force of this spring so that it rotates in the direction P2.
Accordingly, when the data cartridge 1 is not mounted, the pulley 31 is at the position shown by the dotted line in FIG. 8. When the data cartridge 1 is partially mounted, the drive roller 4 comes into contact with the pulley 31 and opposes the spring force so that the pulley 31 is pressed in the upwards direction in FIG. 8. As a result the pulley 31 rotates along with the support member 38 in the direction P1, and when the mounting of the data cartridge 1 is completed, the pulley 31 is in the position shown by the solid line in FIG. 8.
As has already been explained, the pulley 31 is urged, along with the support member 38, so that it rotates in the direction P2, and so when the data cartridge 1 is mounted in the mounting portion 22, the pulley 31 comes into contact with the peripheral surface 4a of the drive roller 4 and the drive roller 4 is pressed in the downwards direction in FIG. 8.
When the drive motor 34 rotates under the conditions described above, the pulley 31 rotates via the belt 36, and the drive roller 4 rotates so that the magnetic tape 5 inside the data cartridge 1 runs. When rotation of the drive motor 34 stops, the rotation of the pulley 31 stops, the rotation of drive roller 4 stops and the running of the magnetic tape 5 stops.
The tape transport mechanism 20 that includes the drive unit 30 described above must have the following conditions satisfied so that the rotational force of the drive motor 34 is efficiently transmitted to the drive roller 4 inside the data cartridge 1 in order to make the magnetic tape 5 run.
First, smooth transmition of the rotational force of the drive motor 34 to the pulley 31 via the belt 36 requires that there be no slipping of the belt 36 with respect to the pulley 31 and the roller 35. Accordingly, in the mounted state of the data cartridge 1, the tensile force that acts on the belt 36 must create a sufficient friction force between the belt 36, the pulley 31 and the roller 35, so that the belt 36 does not slip with respect to the pulley 31 or the roller 35.
Then, in order for the rotational force of the pulley 31 to be smoothly transmitted to the drive roller 4, the magnitude of the pressing force that the pulley 31 exerts on the drive roller 4, in the state where the data cartridge 1 is mounted must be great enough so that a suitably large friction force acts between the pulley 31 and the drive roller 4. At the same time, this pressing force of the pulley 31 with respect to the drive roller 4 must be directed so that it acts in a straight line linking the axial center C1 of the rotating shaft 33 of the pulley 31 and the axial center C2 of the drive roller 4.
The conventional tape transport mechanism 20 is configured so that these conditions are satisfied and the rotational force of the pulley 31 is efficiently transmitted to the drive roller 4.
More specifically, as shown in FIG. 8, in the state where the data cartridge 1 is mounted, the straight line linking the axial center C1 of the rotating shaft 33 of the pulley 31 and the axial center C2 of the drive roller 4, and the straight line linking the axial center C1 of the rotating shaft 33 of the pulley 31 and an axial center C3 of the rotating shaft 37 are substantially perpendicular. Because of this, the contact surface with the drive roller 4 is pressed by the pulley 3, in the direction of a straight line linking the axial center C1 and the axial center C2.
In addition, when the data cartridge 1 is not mounted, the pulley 31 does not contact the drive roller 4 even if it is urged by the spring force, so that it moves in the downwards direction. Then, when the pulley 31 has been urged downwards to the position indicated by the dotted line, the spring force that urged the pulley 31 downwards is balanced by the tension force of the belt 36 that pulls the pulley 31 in the direction of the roller 35. At this time, there is a distance 12 between the axial center C1 of the pulley 31, and the axial center C4 of the rotating shaft 34a of the drive motor 34. Moreover, the belt 36 is made of rubber that has a slight elasticity.
When the data cartridge 1 is mounted in the mounting portion 22, the drive roller 4 comes into contact with the pulley 31 and presses it in the upwards direction as shown in FIG. 8. When the mounting of the data cartridge 1 is completed, as shown by a solid line in FIG. 8, there is a distance 11 between the axial center C1 and the axial center C4. In this state, the belt 36 is contracted by a length that is substantially 2(12-11) shorter than that when the data cartridge 1 is not mounted. As a result, the tension force of the belt 36 that pulls the pulley 31 in the direction of the roller 35 is smaller than in the unmounted state.
The previously described spring force that urges the pulley 31 along the direction P2 is constant; as a result the pressing force of the pulley 31 with respect to the drive roller 4 acts in the direction P2. The magnitude of this pressing force is determined by the spring force of the spring that urges the support member 38 along with the pulley 31, and the tension force of the belt 36 with respect to the pulley 31. At the same time, the friction force of the belt 36 with respect to the pulley 31 and the roller 35 is also determined by the tensile force of the belt 36.
In the conventional tape transport mechanism 20, there is a suitable friction force of the belt 36 with respect to the pulley 31 and the roller 35, and the magnitude of the pressing force of the pulley 31 with respect to the drive roller 4 is set by the spring force of the spring, and the tensile force of the belt 36 is large enough to cause a suitable friction force between the pulley 31 and the drive roller 4.
As is commonly known, the tensile force of the belt 36 changes in magnitude when the length of the belt 36 changes. Accordingly, if the distance 11 between the axial center C1 and the axial center C4 is set to be small, then there will be a large change in the tensile force of the belt 36 if there is a change in the position of the pulley 31. Because of this, if the value for this distance 11 is small, it is difficult to set magnitudes for the spring force of the spring, and for the tensile force of the belt 36 so that the above conditions are satisfied. Therefore, with the conventional tape transport mechanism 20, the configuration is such that this distance 11 can be set so that it is, to a certain degree long, and so that the settings of the spring force of the spring and the tensile force of the belt 36 are facilitated.
However, when the distance 11 between the axial center C1 and the axial center C4 is long, then when the drive motor 34 is placed as shown in FIG. 8, it is difficult for the dimension in the direction of the width of the transport apparatus main unit 21 to be reduced. More specifically, the dimension W1 in the direction of the width of the transport apparatus main unit 21 is greater than the dimension (a+b) that is the sum of the dimension a of the portion of the drive motor 34 extending beyond a guide rail 22a, and a dimension b between the guide rails 22a and 22a.
Thus, when the drive motor 34 is positioned to the rear of the transport apparatus main unit 21 so that the width of the device can be reduced, there is a large change in the distance between the axial center C1 and the axial center C4 when there is a change in the position of the pulley 31, and so it is even more difficult to set the spring force of the spring and the tensile force of the belt 36.